NSF Award
2412046
With support from the Environmental Chemical Sciences Program in the Division of Chemistry at NSF, James Davies of the University of California-Riverside (UCR) and Ryan Davis of Trinity University will study the phase state of mixed organic-inorganic aerosol particles under environmental conditions. Aerosols influence climate as they form the basis of clouds and are engaged in both the scattering and the absorption of sunlight. Aerosols can also negatively affect air quality and provide a vehicle for the spread of airborne disease. The specific environmental impact associated with aerosols depends upon the chemical composition and phase state of the aerosol particles. Inadequate knowledge of the phase state of organic-inorganic aerosols, such as those found in the environment, represents a source of uncertainty in climate and air quality models. Mixed organic-inorganic particles can form a range of phase states depending on environmental conditions; these include liquid and solid phases, and amorphous phases, such as viscous liquids, glasses, and gels. This project will explore the formation of amorphous phase states in aerosol particles and characterizes the properties that determine their impacts in the environment. This collaboration between UC Riverside and Trinity University will facilitate undergraduate and graduate research across both institutions and seeks to provide for an improved understanding of aerosol chemistry across a range of scientific disciplines.<br/><br/>To enhance knowledge of aerosol particles in the environment, this project is a collaborative study between teams at an R1 public university, UC-Riverside--the James Davies research group--and at a predominantly undergraduate liberal arts and sciences university, Trinity University--the Ryan Davis research group--will examine the role of temperature and relative humidity on the phase state and associated properties of internally mixed organic-inorganic aerosol particles. Aerosol particles containing mixtures of organic and inorganic compounds exhibit complex phase behavior in response to changes in relative humidity (RH) and temperature due to hygroscopic interactions. The phase morphology of aerosol particles influences their interactions with light, their response to chemical processing due to changes in viscosity, and their ice and cloud nucleating potential. This proposal will investigate the phase morphology and associated rheological properties of internally mixed organic-inorganic aerosol particles exposed to controlled RH and temperature conditions. The main objectives are: (1) systematically characterize the hygroscopicity and viscosity of particles containing atmospherically-relevant salts and oxygenated organics; (2) determine the temperature and humidity conditions for the onset of phase separation and correlate with molecular composition; and (3) explore the consequences of viscosity and phase separation on the rate of molecular diffusion. To achieve these goals, single particles of aqueous oxygenated organic compounds and atmospherically-relevant mono- and divalent salts will be levitated using an electrodynamic balance. Optical spectroscopy, microscopy and light scattering methods will be used to identify phase separation while new and established characterization methods will be applied to measure hygroscopic growth, viscosity, and diffusive transport. The research will help to motivate the next generation of scientists by exposing undergraduate and graduate researchers to the physically rigorous study and characterization of aerosols in a project that relates more generally to climate science research, an area of great societal interest and importance today.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
